1) Field of the Invention
The present invention relates to an image forming apparatus, a process cartridge, and a development unit.
2) Description of the Related Art
Conventionally, as a color image forming apparatus, there is a tandem type image forming apparatus in which latent images formed on a plurality of photoconductors are manifested in toner images by a developing device for each color, and the toner images are sequentially transferred onto an intermediate transfer belt or a transfer material to form a color image. As an example, forming a color image is realized by sequentially superimposing four color toner images of black (Bk), yellow (Y), magenta (M), and cyan (C) formed on the photoconductors onto the intermediate transfer belt or the transfer material.
Further, an apparatus is known in which a developing device and a device used for an image forming process such as a photoconductor are formed integrally to form a process cartridge, which is integrally detachable from the image forming apparatus. In the case of the tandem type color image forming apparatus, four process cartridges of yellow, magenta, cyan, and black are installed, corresponding to the toner color to be replenished. Heretofore, there has been an instance where a process cartridge was installed by mistake, in a place where a process cartridge for another color was to be installed. In this case, since the toner supplied from the image forming apparatus does not match with the color toner stored in the developing device of the process cartridge, a mismatching color toner may be mixed in the developing device. To prevent such mistake in installation, the structure of a section of the apparatus body where the process cartridge is to be installed (hereinafter, “station”) is made different for each color, thereby preventing a process cartridge from being installed in a section for a mismatching color. Accordingly, the structure itself of the process cartridge should be different for each color, and parts different for each color need to be produced. Hence, it becomes necessary to provide a separate production line and a model of the process cartridge for each color, thereby increasing the production cost.
Therefore, various units have been proposed, to prevent mistakes in installation, even if a common process cartridge is used. Japanese Patent Application Laid-Open No. 2001-83862 (hereinafter, “document (1)”) discloses an apparatus in which a common process cartridge is provided with a storage unit to store the color of toner replenished for the first time. When installed in the station, the process cartridge compares the toner color stored in the storage unit with the toner color recorded in the apparatus body. Thus, if the process cartridge is installed in a station for a different color, the color stored in the storage unit does not match with the color stored in the apparatus body, and the image forming operation is suspended or an alarm is displayed. Further, Japanese Patent Application Laid-Open No. H11-24536 (hereinafter, “document (2)”) discloses a process cartridge common to respective colors in which a seal of a color that is same as the toner color stored in the developing device in the process cartridge is attached to a color identification display section. By this seal, users can recognize the color of the process cartridge, thereby preventing a process cartridge from being installed in a station for a mismatching color. Thus, in documents (1) and (2), a common process cartridge can be used, and it is not necessary to provide a separate production line and a model of the process cartridge for each color, thereby decreasing the production cost. Further, the user does not have to store process cartridges for each color, thereby reducing the user's management load.
However, in the case of the process cartridge in document (1), there is no identification display that can be recognized by the user. Therefore, once the process cartridge is taken out from the apparatus, the user cannot recognize which color toner is stored in the process cartridge. Therefore, the user may install the process cartridge in a station for a mismatching color. Further, in the case of the process cartridge in document (2), there is an identification display, and the user can recognize which color toner is stored in the process cartridge, but there is no detector that detects mistakes in installation. Therefore, if the user erroneously installs a process cartridge in a station for a mismatching color, and executes the image forming operation without noticing the error installation, a mismatching color toner may be mixed in the developing device of the process cartridge.
In view of the above problems, it is an object of the present invention to provide an image forming apparatus and a process cartridge, which avoid erroneous installation by users, and can detect error in installation, if any.
Further, Japanese Patent Application Laid-Open No. 2001-80090 (hereinafter, “(3)”) discloses a unit in which pin holes of a number corresponding to the color types are provided in the process cartridge. By changing the position of a pin to be inserted in the pin hole, the shape of the process cartridge becomes different for each color. Accordingly, the parts can be shared, thereby reducing the production cost. Further, a guide groove is provided for guiding the pin provided in the process cartridge in the insertion direction at a position corresponding to the color. Thus, erroneous installation of the process cartridge is prevented.
However, in (3), error in installation of the process cartridge is prevented by a difference between the shape of the apparatus body and the shape of the process cartridge. Therefore, if the user pushes the process cartridge into the apparatus body without noticing that it is a process cartridge for a different color, the apparatus body may get damaged or the pin may break.